When an aerodyne is flying, it is important that it maintains a steady stable glide. Conventional aerodynes traditionally have the following prerequisites to assure longitudinal equilibrium and stability:
(1) equilibrium of aerodymanic and gravity forces and moments about the aircraft's mass centre; and
(2) means for restoring the aircraft to equilibrium flight when disturbed from the glide path as a result of variations of these forces and moments. Conventionally, this is achieved for aircraft having wing-tail configurations by setting the rear stabilizer at a lower angle-of-attack than the wing, thereby providing a positive longitudinal reflex to the configuration.
Conventional aircraft are also generally fairly rigid in construction and the lift on the aircraft is primarily a function of the attack angle and the speed of the aircraft. With increasing speeds, lift increases pulling the airplane into a nose-up trajectory.
According to the present invention, an aerodynamic structure having longitudinal equilibrium and stability is provided without requiring essentially any longitudinal reflex because the centre of drag is above the structure's mass centre. The structure comprises first and second essentially identical planar sections hingedly connected at their roots to one another at dihedral angles. The sections are moveable in unison to vary the angle between each section and its transverse axis to alter the equilibrium flight angle and the degree of longitudinal stability.
According to one aspect of the invention and as opposed to conventional aircraft, the lift on the structure of the present invention decreases with increasing speed beyond a predetermined speed. Furthermore, when using a wing-tail configuration, no longitudinal reflex is required between the forward wing and the rear stabilizer to achieve longitudinal equilibrium and static longitudinal stability.